<colgroup> rendering rules should only apply if it's styled as a colgroup

[zcorpan]

From #1799

 <p>For the purposes of the CSS table model, the <code>colgroup</code> element, if it contains no
  <code>col</code> element, is expected to be treated as if it had as many such children as its
  <code data-x="attr-colgroup-span">span</code> attribute <span data-x="rules for parsing non-negative
  integers">specifies</span>.</p>

@bzbarsky

The ruby/colgroup parts are simply nonsense, imo. The HTML spec should simply define the default UA styling for those (setting the display) property and say nothing else. I guess you still have to define what span means on colgroup, but that should be restricted to cases when the colgroup is in fact styled as a colgroup, and should explicitly talk about child table-column boxes somewhere, not child elements.

If I style my <colgroup> as display: table-row-group then none of the stuff quoted above should apply, of course.